Conventional photonic crystal (PC) laser diodes (LD) have used an oscillation in a Γ-point (gamma-point) band edge of photonic band structure.
The Γ-point (gamma-point) oscillation has a function for forming standing waves for an oscillation of periodic structure in the PC, and a function for extracting the light as outputs, to a PC layer by diffracting the light in a surface vertical direction (e.g., refer to Patent Literatures 1-3.).